The case alleges $4.3 million was skimmed off the Metro Courthouse construction project. A group of defendants, including former state Sen. Manny Aragon, allegedly submitted false or inflated invoices, then split the proceeds.

Engineer Raul Parra pleaded guilty to two counts of mail fraud and one count of conspiracy.

He's agreed to testify at trial of others accused in the scandal, if those trial takes place.

When sentenced, Parra could get up to 20 years in prison and have to pay up to a $250,000 fine.

Earlier Tuesday, the wife of former court administrator Toby Martinez, Sandra Martinez, pleaded guilty to one count of knowing about a felony and not reporting to authorities.

Her husband pleaded guilty to mail fraud and conspiracy charges in connection with this case last week.